Infectious Diseases of Ferrets

Ferrets can be infected by a variety of microorganisms, including bacteria, viruses, fungi, and parasites. Some of these can also infect other types of pets and people.

Bacterial Diseases

Helicobacter mustelae is found in the stomach and in the small intestines of most, if not all, ferrets after weaning. It can cause chronic, persistent inflammation of the stomach (common in ferrets over 4 years of age) and cause ulcers similar to those found in humans. Gastric lymphoma, a stomach cancer, may occur in chronic cases. Signs include lack of appetite, vomiting, teeth clenching or grinding, diarrhea, stools stained black by blood, increased salivation, and abdominal pain. Lethargy, weight loss, and dehydration can also occur. An accurate diagnosis requires a biopsy and tests on the tissue collected, but often a suspected diagnosis can be made based on the history and the signs of the ferret. Treatment is with multiple antibiotics and usually lasts for 21 days.

Lawsonia intracellularis can cause a bowel disease characterized by excessive growth of intestinal tissue, especially in younger ferrets. Acute cases are often associated with stress. Signs include diarrhea, weight loss, and rectal prolapse, in which the rectum protrudes out of the anus and can be damaged or prevent defecation. Treatment is with antibiotics for 14 to 21 days.

Other bacterial infections seen in ferrets are similar to those seen in other mammals like dogs and cats and are treated similarly.

Viral Diseases

Ferrets are extremely susceptible to canine distemper virus. The disease affects multiple organs and damages the immune system. The virus can be transmitted by direct or indirect contact with an infected animal. It can be carried on the air, or on shoes, clothes, and skin. Signs are seen 7 to 10 days after infection, starting with fever and a rash on the chin and groin area. This is followed by loss of appetite and thick discharge of mucus and pus from the eyes and nose. Brown crusts on the face and eyelids and thickening of the footpads also occur. Respiratory signs such as coughing, sneezing, and difficulty breathing can develop and progress rapidly. Canine distemper is fatal in ferrets. Death typically occurs 12 to 14 days after infection. There is no remedy or treatment. The best defense is yearly vaccination.

Epizootic catarrhal enteritis is an inflammation of the intestines that is highly contagious. Ferrets usually contract the disease when a new, apparently healthy juvenile ferret is introduced into the home, or when exposed to contaminated objects such as food bowls, bedding, or clothing. The disease is most severe in older ferrets, which may take months to recover. Signs develop in 2 to 14 days and include lack of appetite; green, watery, or slimy diarrhea; stools stained black by blood; dehydration; lethargy; and weight loss. The virus damages the hair-like projections called villi that line the intestines, making it difficult for the affected animal to properly digest and absorb food.

It is not easy to accurately diagnose the virus; an intestinal biopsy is required. Treatment includes supportive care such as fluids, nutritional support (usually a bland, easily digestible diet), antibiotics, and substances that coat the intestines to protect their surface.

To avoid spreading the disease, wash hands and change clothes and shoes after handling any young or infected ferret before going near unaffected ferrets. Wash any new toy or bedding before giving it to your ferrets. Clean the litter box of the infected ferret at least daily. New ferrets brought into the home must be quarantined for at least 1 month.

Aleutian disease is a viral infection originally seen in mink, but at least 2 distinct ferret strains of the virus have been identified. The virus causes the ferret's antibodies to attack its own organs. The affected organs become inflamed and have difficulty functioning properly. The result is a variety of vague signs such as weight loss, weakness, clumsiness, an enlarged liver, and an enlarged spleen. Your veterinarian will make a diagnosis based on these signs and high levels of antibodies in the blood. No specific treatment exists. An infected ferret must be isolated to prevent the spread of the disease, and strict hygiene measures are recommended at all times.

Fungal Diseases

Ferrets are susceptible to ringworm, most commonly contracting 1 of 2 types, Microsporum canis or Trichophyton mentagrophytes. Transmission is by direct contact or contact with contaminated objects such as bedding or a grooming brush. It is often associated with overcrowding and exposure to cats. Infection is more common in infant and young ferrets. It is possible to transfer ringworm between people and ferrets. Wear gloves when handling an infected animal, and wash hands thoroughly afterward.

Diseases that can be Spread from Ferrets to People

Influenza

Rabies

Ringworm

Other fungal diseases, such as fungal pneumonia (blastomycosis) and fungal infections of the central nervous system (cryptococcal meningitis), are very unusual in ferrets but have been reported.

Parasites

Ear mites are the most common parasite found in ferrets. The same organism is found in dogs and cats, and the disease can be passed between these species. Ferrets with dark, grayish ear wax and unpleasant smelling ears probably have ear mites. In many cases, there are no signs at all, and the mites are only discovered during a routine physical exam. A veterinarian will take a sample of the material in the ear and look at it under a microscope to diagnose ear mites. The drug ivermectin is commonly used for treatment.

Fleas are occasionally seen in ferrets, especially in households with multiple pets. They can be transmitted between ferrets, dogs, and cats. A large, untreated flea infestation can decrease red blood cells and cause weakness in ferrets. The most effective flea control products are available only through veterinarians. Many of the long-acting topical treatments last longer in ferrets because of the increased oily secretion in the coat. To rid an environment of fleas, thoroughly clean ferret cages and bedding, as well as the rugs, carpet, and furniture. Talk to your veterinarian about treating the entire environment (house or room) to get rid of fleas.

Mange (scabies) in ferrets is caused by a microscopic mite known as Sarcoptes scabiei and comes in 2 types. The first is a generalized inflammation of the skin that causes hair loss and severe itching. Red, raised areas filled with pus may develop. Ferrets scratch the affected area in an attempt to relieve the itch, quickly leading to damaged skin, secondary infection, and sores. The second form of the disease is limited to the feet, toes, and pads. The feet become red, swollen, and painful. It is also accompanied by intense itching.

Mange is caused by mites. It can cause hair loss and severe itching in ferrets.

The standard method of testing for mange is to take a skin scraping and identify the mites under a microscope. However, a negative scraping does not mean a ferret does not have mange. Diagnosis may be based on history and the response to scabies medication. Mange can be treated by the drug ivermectin. Antibiotics may be needed to treat infections caused by scratching.

Ferrets that are housed outside may be infested with bot fly larvae. The larvae burrow into the skin, incubate for 30 days, then burrow back out and fall to the ground, leaving an open wound. In rare cases, the larvae burrow their way into the brain, nasal passages, or eyelids. Wounds are typically visible around the head, neck, and trunk, and may ooze pus. A veterinarian will open the pocket where the larvae have burrowed, pull out the larvae, and clean the wound.

Heartworm disease is a mosquito-transmitted illness seen primarily in dogs (see Heart and Blood Vessel Disorders of Dogs: Heartworm Disease in Dogs). It can be found in ferrets, especially those given outdoor access in areas where heartworms are common. Once inside the ferret, the worm travels to the heart where it grows and eventually interferes with heart functions. Heartworms may also block the pulmonary arteries and cause respiratory problems. Because of a ferret's small size, even a single worm can cause disease and death. Signs include lethargy, coughing, difficulty breathing, and a buildup of fluid in the abdomen. Ferrets are at high risk of sudden death from heartworm disease. The disease may be difficult for your veterinarian to detect because of the relatively small number of worms present. Treatment is longterm and involves using drugs to prevent blood clots and kill the adult worms.

Heartworm disease is much easier to prevent than treat. In areas where heartworms occur, ferrets should be given an appropriate dose of a heartworm preventive medication, which can be obtained from your veterinarian. The drugs selamectin and ivermectin are commonly used to prevent heartworm disease. Keeping ferrets indoors will limit their exposure to mosquitoes that transmit heartworms.

Coccidiosis affects the lining of the intestines and can cause disease in young ferrets. Signs include diarrhea, lethargy, and rectal prolapse. Treatment is with antibiotics. If present, rectal prolapse usually resolves itself after the underlying disease is treated. Over-the-counter creams used to treat hemorrhoids may be helpful in treating rectal prolapse.

Last full review/revision July 2011 by James K. Morrisey, DVM, DABVP (Avian)